CARNELIAN, a red variety of chalcedony, much used as an
ornamental stone, especially for seals. The old name was
cornelian, said to have been given in reference either to the
horny appearance of the stone (Lat. cornu, “horn”) or to its
resemblance in colour to the berry of the cornel; but the original
word was corrupted to carneliun, probably in allusion to its
reddish colour (carneus, “flesh-coloured”). Some carnelian,
however, is brown, yellow or even white. Certain kinds of
brown and bright red chalcedony, much resembling carnelian,
pass under the name of sard (q.v.). The Hebrew odem was
probably a red stone, either carnelian, sard or jasper. All
carnelian is translucent and is thus distinguished from jasper
of similar colour, which is always opaque. The red colour of
typical carnelian is due to the presence of ferric oxide. This is
often developed artificially by exposure to sunshine, or to
artificial heat, whereby any ferric hydrate in the stone becomes
more or less dehydrated; or the stone is treated with a solution
of an iron salt, like ferrous sulphate, and then heated, when
ferric oxide is formed in the pores of the stone. An opaque
white surface is sometimes produced artificially on a red
carnelian: this is said to be done by coating the stone with
carbonate of soda and then placing it on a red-hot iron; or by
using a mixture of potash, white lead and certain vegetable
juices, and heating it on charcoal. Inscriptions and figures in
white on red carnelian (“burnt carnelian”) are well known from
the East. Much carnelian comes from India, being mostly
derived from agate-gravels, resulting from the disintegration of
the Deccan traps, in the neighbourhood of Ratanpur, near
Broach. A good deal of the carnelian now sold, however, is
Brazilian agate, artificially stained. (See Agate.)